1. Field of the Invention
The invention relates generally to the field of apparatus used in the manufacture of integrated circuits, and more particularly to an arrangement for inhibiting bacterial and algal contamination in the water supply used in the manufacturing process. The invention provides a new and improved deionized liquid spray gun in which the liquid flows continuously to eliminate the stagnation of the water which is conducive to bacterial and algal growth.
2. Description of the Prior Art
Modern society depends on the reliability of many types of semiconductor devices. In order to meet the vast need for such devices, manufacturing facilities fabricate thousands of semiconductor devices simultaneously. Such large scale fabrication is accomplished by creating hundreds of devices on a single wafer of silicon and handling many wafers at one time. A problem with any portion of the manufacturing process will result in the manufacture of a large number of devices which may prove unreliable in use, if they work at all. One of the problems that confronts the manufacturer of semiconductor devices is contamination of the wafers. The nature of semiconductors makes them highly susceptible to contamination in any form and one source of contamination is the deionized water supply.
A semiconductor device is fabricated in a number of sequential process steps by impregnating specific ions, called impurities, into a silicon wafer. The nature and amount of impurities must be strictly controlled if the device is to function properly. Water is used between the processing steps to wash the wafers and that water must be free of ions so as not to introduce ions beyond those required by the process.
To prevent the growth of bacteria or algae in the tubing which distributes the deionized water to the fabrication areas, the water is kept in constant flow. When the water is not being used, the plumbing permits the deionized water to be returned to the deionized water supply. This distribution system is referred to as a continuous flow loop.
Each fabrication area has deionized water supplied to spray guns for general use such as rinsing the silicon wafers. A problem arises in that these spray guns do not contain continuous flow loops. As a result, the water in the tube leading to the gun and the water remaining in the gun itself is stagnant when the gun is not in use. Stagnant water is an ideal medium for growth of bacteria and algae so that when the gun is eventually used, the bacteria, algae and their metabolic products which are formed within the gun contaminate the deionized water flowing through it. Although maintaining a continuous flow loop up to the inlet of the gun reduced bacterial and algal growth in the water supply tube, it did nothing to reduce the growth of bacteria and algae within the gun itself.